Speak softly and carry a big stick
The world is a dangerous place, with dangerous people in it. Self-defense is a necessity. Internally, this means police, courts, judges, juries, jails, prisons, and mental hospitals. Externally, this means a standing military and all its accoutrements.
A society has all kinds of people in it, and a just society would make room for all of them, including those most inclined to be of the warrior mentality. We need protection, they need a job --- voila! --- police, jailers, military.
Where we need to be very careful is in deciding exactly when to call on the services of our professional warriors, and just how often. It's a resource that most definitely needs to be under-utilized. Diplomacy, negotiation, gentle guidance, often just carefully watching and analyzing a situation; all these need to be tried first.
One would have thought that the Constitution had established some checks on our powers to wage war, but between those of us who want to be kept safe and secure from every imaginable danger all the time and those of us who want to be warriors by proxy [not to mention those who expect to profit from conflict], we've instead over-utilized this resource, and stretched it to the breaking point.
Not to mention all the people we've killed and all the havoc we've now wreaked on a few other societies, none of which were an imminent threat to us.
Then there's the war on drugs, but you get the picture.